Method of producing ingot with variable composition using planar solidification

ABSTRACT

Molten metal of a first composition is fed into a mold cavity, via a first control apparatus, wherein the control apparatus is open, wherein the feeding comprises flowing out of a first feed chamber. The first control apparatus is closed. A second control apparatus is opened. Molten metal of a second composition is fed into the mold cavity, via the second control apparatus, wherein at least a portion of the metal of the first composition in the mold cavity is sufficiently molten so that an initial feed of molten metal of the second composition mixes with the molten metal of the first composition in the mold cavity, wherein the feeding comprises flowing out of a second feed chamber, wherein the second composition is different from the first composition. An ingot is removed from the mold cavity, wherein the ingot has a top section, a middle section, and a bottom section, wherein the bottom section is composed of metal of the first composition, wherein the top section is composed of metal of the second composition, wherein the middle section is composed of a mixture of metal of the first composition and the second composition.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/180,391 filed May 21, 2009, which is incorporated herein byreference in its entirety.

SUMMARY

A method of casting metal wherein planar, directional solidification iscombined with feeding metal of varying composition to produce an ingotwith varying composition through the ingot thickness and substantiallyuniform composition across the ingot width and thickness.

A method of casting metal, comprising the following steps. Molten metalof a first composition is fed into a mold cavity, via a first controlapparatus, wherein the control apparatus is open, wherein the feedingcomprises flowing out of a first feed chamber. The first controlapparatus is closed. A second control apparatus is opened. Molten metalof a second composition is fed into the mold cavity, via the secondcontrol apparatus, wherein at least a portion of the metal of the firstcomposition in the mold cavity is sufficiently molten so that an initialfeed of molten metal of the second composition mixes with the moltenmetal of the first composition in the mold cavity, wherein the feedingcomprises flowing out of a second feed chamber, wherein the secondcomposition is different from the first composition. An ingot is removedfrom the mold cavity, wherein the ingot has a top section, a middlesection, and a bottom section, wherein the bottom section is composed ofmetal of the first composition, wherein the top section is composed ofmetal of the second composition, wherein the middle section is composedof a mixture of metal of the first composition and the secondcomposition.

A method of casting metal, comprising the following steps. Molten metalof a first composition is fed into a mold cavity, via a first controlapparatus, wherein the control apparatus is open, wherein the feedingcomprises flowing out of a first feed chamber. The first controlapparatus is closed. A second control apparatus is opened. Any moltenmetal of the first composition between the first feed chamber and thefirst control apparatus is drained, Molten metal of a second compositionis fed into the mold cavity, via the second control apparatus, whereinat least a portion of the metal of the first composition in the moldcavity is sufficiently molten so that an initial feed of molten metal ofthe second composition mixes with the molten metal of the firstcomposition in the mold cavity, wherein the feeding comprises flowingout of a second feed chamber, wherein the second composition isdifferent from the first composition. A first thickness of metal in themold cavity is determined. The second control apparatus is closed inresponse to determining the first thickness. A second thickness of metalin the mold cavity is determined. The first control apparatus is openedin response to determining the second thickness. Molten metal of thefirst composition is fed into the mold cavity, wherein at least aportion of the metal of the second composition in the mold cavity issufficiently molten so that an initial feed of molten metal of the firstcomposition mixes with the molten metal of the second composition in themold cavity. An ingot is removed from the mold cavity, wherein the ingothas a first layer, a second layer, a third layer, a fourth layer, and afifth layer wherein the first and fifth layers are composed of metal ofthe first composition, wherein the third layer is composed of metal ofthe second composition, wherein the second and fourth layers arecomposed of a mixture of metal of the first composition and the secondcomposition.

As used herein, a solidification front is, for example, the interfacebetween the solid portion and liquid portion of a cast ingot as itcools. A substantially planar solidification front is, for example, asolidification front that is substantially uniform across the planesubstantially parallel to the face of the ingot that begins coolingfirst.

A cast metal ingot is formed, wherein a solidification front remainssubstantially planar during casting, wherein the ingot has a topsection, a middle section, and a bottom section, wherein the bottomsection is composed of metal of a first composition, wherein the topsection is composed of metal of a second composition, wherein the middlesection is composed of a mixture of metal of the first composition andthe second composition.

A cast metal ingot is formed, wherein a solidification front remainssubstantially planar during casting, wherein the ingot has a firstlayer, a second layer, a third layer, a fourth layer, and a fifth layerwherein the first and fifth layers are composed of metal of a firstcomposition, wherein the third layer is composed of metal of the secondcomposition, wherein the second and fourth layers are composed of amixture of metal of the first composition and the second composition.

A cast metal ingot is formed, wherein a solidification front remainssubstantially planar during casting, wherein the ingot has multiplelayers comprising two or more compositions separated by layers composedof mixtures of those compositions.

A method of casting metal, comprising the following steps. A specifiedquantity of molten metal of a first composition is fed into a mixingapparatus. Molten metal is fed from the mixing apparatus into a moldcavity. A molten metal of a second composition is fed into the mixingapparatus, wherein the first composition is different from the secondcomposition. An ingot is removed from the mold cavity, wherein the ingothas a thickness, a top, and a bottom, wherein the ingot compositionincludes a continuous gradient, wherein the continuous gradient is agradient of metals of at least the first and second compositions,wherein an amount of metal of the first composition decreases graduallyfrom the bottom of the ingot through the thickness to the top of theingot, wherein an amount of metal of the second composition in increasesgradually from the bottom of the ingot through the thickness to the topof the ingot.

A metal ingot is cast from at least two different metals, including afirst composition and a second composition, wherein a solidificationfront remains substantially planar during casting, wherein the ingot hasa thickness, a top, and a bottom, wherein the ingot composition includesa continuous gradient, wherein the continuous gradient is a gradient ofmetals of at least the first and second compositions, wherein an amountof metal of the second composition decreases gradually from the bottomof the ingot through the thickness to the top of the ingot, wherein anamount of metal of the first composition in increases gradually from thebottom of the ingot through the thickness to the top of the ingot.

A method of casting metal, comprising the following steps. Molten metalof a first composition is fed into a mold cavity via a firstprogrammable control apparatus, wherein the feeding comprises flowingout of a first feed chamber. Molten metal of a second composition is fedinto the mold cavity via a second programmable control apparatus,wherein the feeding comprises flowing out of a second feed chamber,wherein the second composition is different from the first composition.The first control apparatus is programmed to permit molten metal of thefirst composition to flow out of the first feed chamber at a desiredrate that decreases to 0 lbs/minute during a desired first castingperiod. The second control apparatus is programmed to permit moltenmetal of the second composition to flow out of the second feed chamberat a rate increasing from 0 lbs/minute to the desired rate. The firstcontrol apparatus is also programmed to permit molten metal to flow outof the first feed chamber at a rate increasing from 0 lbs/minute to thedesired rate, during a desired second casting period. The second controlapparatus is also programmed to permit molten metal to flow out of thesecond feed chamber at a rate decreasing from the desired rate to 0lbs/minute during the second casting period. An ingot is removed fromthe mold cavity, wherein the ingot has a thickness, a top, a bottom, anda mid-point, wherein the ingot composition includes a continuousgradient, wherein the continuous gradient is a gradient of metals of thefirst and second composition, wherein an amount of metal of the firstcomposition decreases gradually from the bottom of the ingot through thethickness to the mid-point of the ingot, wherein an amount of metal ofthe first composition increases gradually from the mid-point of theingot through the thickness to the top of the ingot.

A metal ingot is cast from at least two different metals, including afirst composition and a second composition, wherein a solidificationfront remains substantially planar during casting, wherein the ingot hasa thickness, a top, a bottom, and a mid-point, wherein the ingotcomposition includes a continuous gradient, wherein the continuousgradient is a gradient of metals of at least the first and the secondcomposition, wherein an amount of metal of the first compositiondecreases gradually from the bottom of the ingot through the thicknessto the mid-point of the ingot, wherein an amount of metal of the firstcomposition increases gradually from the mid-point of the ingot throughthe thickness to the top of the ingot.

Other variations, embodiments and features of the present disclosurewill become evident from the following detailed description, drawingsand claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of an illustration of one embodiment of the castingsystem of the present invention.

FIG. 2 is a top view of an illustration of another embodiment of thecasting system of the present invention.

FIG. 2 a is a top view of an illustration of a further embodiment of thecasting system of the present invention.

FIG. 3 is a cutaway front view of an illustration of an example of thecasting apparatus including the mold cavity of an embodiment of thecasting system of the present invention.

FIG. 4 is a top view of an illustration of one embodiment of the castingsystem of the present invention.

FIG. 5 is a top view of an illustration of another embodiment of thecasting system of the present invention.

FIG. 6 is a top view of an illustration of a further embodiment of thecasting system of the present invention.

FIG. 7 represents an ingot composition profile for an embodiment of thepresent invention.

FIG. 8 represents an ingot composition profile for another embodiment ofthe present invention.

FIG. 9 represents an ingot composition profile for yet anotherembodiment of the present invention.

FIG. 10 represents an ingot composition profile for a further embodimentof the present invention.

FIG. 11 represents a cast metal ingot profile for an embodiment of thepresent invention.

FIG. 12 represents a cast metal ingot profile for an embodiment of thepresent invention.

FIG. 13 represents a cast metal ingot profile for an embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE DISCLOSURE

It will be appreciated by those of ordinary skill in the art that theembodiments disclosed herein can be embodied in other specific formswithout departing from the spirit or essential character thereof. Thepresently disclosed embodiments are therefore considered in all respectsto be illustrative and not restrictive.

In one embodiment of the present invention, a cast ingot is formed by amethod of unidirectional solidification wherein the composition isvaried through the thickness, either gradually or in steps or anycombination of the two. For purposes of this description, thickness isdefined as the thinnest dimension of the casting. A casting system usedto produce the ingot includes, in one embodiment, a casting apparatusincluding a mold cavity oriented substantially horizontally, having aplurality of sides and a bottom that may be structured to selectivelypermit or resist the effects of a coolant sprayed thereon. One exampleof a bottom configuration is a substrate having holes of a size thatallow coolants to enter but resist the exit of molten metal. Such holesare, in one example, at least about 1/64 inch in diameter, but not morethan about one inch in diameter. Another example of a bottomconfiguration is a conveyor having a solid section and a mesh section.One example of a casting apparatus that may be used is described in U.S.Pat. Nos. 7,377,304 and 7,264,038. By this reference, the contents ofthese patents are deemed to be incorporated into the presentapplication.

In one embodiment of the casting system, a trough for transportingmaterial from each of at least two reservoirs leads to a mixer or astandard degassing unit, each trough having a flow control valve to varythe flow of material from the reservoir into a mixer or standarddegassing unit. In one example, at least one trough leads from the mixerto a degassing unit and a filter, from which the trough terminates at aside of the mold cavity, and is structured to introduce material to themold cavity in a level fashion. In another embodiment, the material isdelivered vertically to the top of the mold cavity in a controlledmanner. In either of these embodiments, the material may be delivered ata single point or multiple points around the mold cavity.

The sides of the mold cavity are in one embodiment insulated. Aplurality of cooling jets, for example air/water jets, are located belowthe bottom, and are structured to spray coolant against the bottomsurface of the substrate. In one embodiment, the substrate is perforatedallowing the cooling media to directly contact the solidifying ingot.

In one embodiment, molten metal is introduced substantially uniformlythrough the mold cavity. At the same time, for example, a cooling mediumis applied uniformly over the bottom side of the substrate. In anotherembodiment, the rate at which molten metal flows into the mold cavity,and the rate at which coolant is applied to the bottom are bothcontrolled to provide unidirectional solidification. The coolant maybegin as air, for example, and then gradually be changed from air to anair-water mist, and then to water but any cooling media or deliverymethod that achieves the desired heat transfer can be used.

Accordingly, one embodiment of the present invention provides animproved method of directionally solidifying castings during coolingwhere the solidification front remains substantially planar. Hence, inone example, as composition of the metal fed into the mold cavityvaries, the composition of the resultant ingot varies in a consistentway through the thickness. In this example, the composition variesthrough the thickness but not across the width or length of the ingot.

In one embodiment, by varying the flow of material from each reservoir,the composition of the ingot can be varied gradually or in a layeredmanner. The following examples result in an ingot having layers ofdifferent compositions, with an interface between the layers that isrelatively sharp, compared to the next group of examples. In oneexample, material of a first composition flows out of the firstreservoir and then is halted at the same time that the flow of materialhaving a second composition is initiated from the second reservoir. Inthis example the resultant ingot consists of a layer of the firstcomposition combined with a layer of the second composition.

In another example, molten metal of the first composition flows from afirst reservoir into a first degasser or other means for removinghydrogen or other undesirable elements from the molten metal, including,for example, sodium, potassium, or calcium. The degasser can be locatedin the casting line, such as a porous trough degasser or a compactdegasser. Alternatively, the degasser can treat the molten metal outsideof the casting line and the molten metal is transferred back into thecasting line.

In a further example molten metal of the first composition next flowsfrom the degasser into a filter, such as for example a ceramic foamfilter or other means for removing nonmetallic inclusions, for exampleoxides.

In another example, molten metal of the first composition flows into themold cavity through a trough including a first control apparatus orsimilar device that regulates the flow rate of the molten metal. Thecontrol apparatus may be, for example, a pneumatic gate or dam, and canbe computer-controlled and/or programmable. In another example, thetrough leading to the mold cavity contains a second control apparatus orsimilar device, through which molten metal of the second compositionflows into the mold cavity.

In a further example, the mold cavity is vertically moveable, and canmove downward during casting at a controllable or programmable rate. Inone embodiment, this rate is about 0.5 inches/minute. In anotherexample, the troughs are vertically moveable, and can move upward duringcasting at a controllable or programmable rate.

In another example, flow from each reservoir is alternated repeatedlyand in any pattern desired, resulting in a multi-layered ingot. Theflows are started and stopped by opening and closing the first andsecond control apparatuses as needed. The control apparatuses may beopened and closed, for example, by computer-controlled pneumatics. Inyet another example, flow from each reservoir is varied, resulting in avariable composition in a first increment of thickness and then flow isstopped from one of the reservoirs to produce a layer of constantcomposition in the next increment of thickness. In a further example,molten metal of the first composition is drained from any trough betweenthe first feed chamber and the first control apparatus before the secondcontrol apparatus is opened to permit the flow of molten metal of thesecond composition into the mold cavity. In another example, moltenmetal of the second composition is drained from any trough between thesecond feed chamber and the second control apparatus before the firstcontrol apparatus is re-opened, re-feeding molten metal of the firstcomposition into the mold cavity.

Suitable alloy compositions include, but are not limited to, alloys ofthe AA series 1000, 2000, 3000, 4000, 5000, 6000, 7000, or 8000. Othersuitable metals may include magnesium base alloys, iron base alloys,titanium base alloys, nickel base alloys, and copper base alloys. New:Suitable alloy compositions further include but are not limited toaluminum alloys containing copper, magnesium, silicon, zinc, lithium,manganese, zirconium, hafnium, scandium, iron, all of which may havevarying weight-percents of the non-aluminum element.

FIG. 9 represents an example of an ingot having two substantially lineargradients through its thickness. As used herein, a substantially linearrate is represented by a substantially constant rate of change.

FIG. 10 represents an example of an ingot having a substantiallyexponential gradient through its thickness.

In one example, the first composition is a 5456 alloy. About 5000 lbs ofthe first composition is held in a furnace at about 1370° Fahrenheit.The second composition is a 7085 alloy. About 6000 lbs of the secondcomposition is held in a furnace at about 1370° Fahrenheit. The moltenmetal of the first composition flows from the first furnace-reservoir tothe first degasser at a rate of about 80 lbs/minute. The degasserrotates at a constant speed as molten metal is transferred out of thefurnace-reservoir. The molten metal of the second composition flows fromthe second furnace-reservoir to the second degasser, and the secondfilter, then stops at the closed second control apparatus. After athickness of solidified metal of the first composition is in the moldcavity, the first control apparatus is closed. The flow out of a feedchamber such as a furnace-reservoir may be stopped, for example, byusing a refractory-type plug or similar device to plug the opening inthe feed chamber through which the molten metal is flowing.Alternatively, the flow out of a feed chamber such as a tilt furnace maybe stopped, for example, by tilting the reservoir. The molten metal ofthe first composition that has flowed out of the first furnace-reservoirbut did not flow into the mold cavity is drained out, and the firstfilter replaced. Next, the second control apparatus is opened, andmolten metal of the second composition flows into the mold cavity at arate of about 80 lbs/minute. After a thickness of solidified metal ofthe second composition is in the mold cavity, the second controlapparatus is closed, and the flow of molten metal out of the secondfurnace-reservoir is stopped. Concomitant with closing the secondcontrol apparatus and stopping the flow out of the secondfurnace-reservoir, the first furnace-reservoir is re-opened and moltenmetal of the first composition flows to the first degasser, then throughthe first filter that is replaced, then stops at the closed firstcontrol apparatus. When the thickness of the solidified metal in themold box is sufficient, the first control apparatus is opened and moltenmetal of the first composition flows into the mold cavity. Castingcontinues until a desired thickness of metal is in the mold cavity. Theresulting ingot has a composition alternating between metal of the firstand second compositions.

FIG. 8 represents a sample composition profile for an ingot of thisembodiment. The first and third layers composed primarily of a 5456alloy have lower tensile strength and higher corrosion resistance withthe second layer composed primarily of a 7085 alloy having a highertensile strength, providing a material that could be useful.

The following examples result in an ingot having layers of differentcompositions, with an interface between the layers that is relativelydiffuse, compared to the preceding group of examples. In one example,material is fed from both reservoirs, simultaneously, resulting in acomposition that is a mix of the compositions in each reservoir relatedto the material flow rates from each reservoir. In another example, theflow from each reservoir is varied continuously to create any desiredmixture at any given position through the thickness of the solidifiedingot. In yet another example, flow from each reservoir is variedresulting in a variable composition in a first increment of thicknessand then flow is stopped from one of the reservoirs to produce a layerof constant composition in the next increment of thickness. Such aprocedure could be varied, in other examples, in any way desired toproduce alternating layers of gradient compositions, constantcompositions or any combination, therein.

Another embodiment of the invention provides a method of maintaining arelatively constant solidification rate through the thickness of thecasting by varying application of the cooling media.

In one example, molten metal of a first composition is an aluminum alloythat is 6 weight percent magnesium. About 6000 lbs of molten metal ofthe first composition is in a furnace-reservoir at about 1370°Fahrenheit. Molten metal of the second composition is an aluminum alloythat is 2.5 weight percent magnesium. About 700 lbs of molten metal ofthe second composition is in a mixing apparatus at about 1350°Fahrenheit. The furnace-reservoir is opened, permitting molten metal ofthe first composition to flow into the mixing apparatus at a rate ofabout 80 lbs/minute. Molten metal flows out of the mixing apparatus intoa filter, and into the mold cavity. Casting continues with molten metalflowing from the furnace-reservoir into the mixing apparatus, from themixing apparatus into the filter, and from the filter into the moldcavity until metal in the mold cavity reaches the desired thickness. Theresulting ingot has a single composition gradient through the thickness,for example the magnesium content. In another example, the mixingapparatus is a degasser that rotates at a constant speed.

FIG. 7 represents a sample composition profile for an ingot of thisembodiment. The portion of the ingot having a lower concentration ofmagnesium has a lower tensile strength, and the portion of the ingothaving a higher concentration of magnesium has a higher tensilestrength.

In another example, molten metal of a first composition is an aluminumalloy that is 2 weight percent magnesium. About 5000 lbs of molten metalof the first composition is in a first furnace-reservoir at about 1370°Fahrenheit. Molten metal of a second composition is an aluminum alloythat is 5 weight percent magnesium. About 5000 lbs of molten metal ofthe second composition is in a second furnace-reservoir at about 1370°Fahrenheit. A first programmable control apparatus between the firstfurnace-reservoir and a degasser located in the casting line isprogrammed to permit molten metal of the first composition to flow outof the first furnace-reservoir into the degasser at a rate decreasingfrom, for example, 80 lbs/minute to 0 lbs/minute during a first castingperiod, for example 16 minutes. The first casting period is determinedby determining a first desired thickness of metal to flow into the moldcavity, for example 8 inches. The rate may decrease, for example,linearly, exponentially, or parabolically. The first control apparatusis also programmed to permit molten metal of the first composition toflow out of the first furnace-reservoir into the degasser at a rateincreasing from 0 lbs/minute to the original rate at which molten metalof the first composition flowed out of the first furnace-reservoir, forexample 80 lbs/minute, during a second casting period, for example, 16minutes. The second casting period is determined by determining a seconddesired thickness of metal to flow into the mold cavity, for example 8inches. The rate may increase, for example, linearly, exponentially, orparabolically. The second control apparatus is programmed to permitmolten metal of the second composition to flow out of the secondfurnace-reservoir into the degasser at a rate increasing from 0lbs/minute to, for example, the maximum rate at which molten metal ofthe first composition is permitted to flow, for example 80 lbs/minute,during the first casting period. The rate may increase, for example,linearly, exponentially, or parabolically. The second control apparatusis also programmed to permit molten metal of the second composition toflow out of the second furnace-reservoir into the degasser at a ratedecreasing from the maximum rate attained, for example 80 lbs/minute, to0 lbs/minute during the second casting period. The rate may decrease,for example, linearly, exponentially, or parabolically. When castingbegins, the control apparatuses function as programmed, and molten metalflows out of the furnace-reservoirs, into a degasser, into a filter, andinto the mold cavity. Casting continues until the metal in the moldcavity reaches a total desired thickness, for example 16 inches. Theresulting ingot has a continuous gradient composition across thethickness, for example the magnesium content.

FIG. 9 represents a sample composition profile for an ingot of thisembodiment.

In a further example, molten metal of a first composition is a 5456alloy or another aluminum alloy that is approximately 4-5 weight percentmagnesium. Molten metal of the second composition is a 7055 aluminumalloy. Casting begins with molten metal of the first composition flowingfrom a furnace-reservoir through the casting system to the mold cavity.Casting continues with molten metal of the second composition flowingfrom a furnace-reservoir through the casting system to the mold cavity.The resulting ingot has a single composition gradient through thethickness, for example the magnesium content. FIG. 7 represents a samplecomposition profile for an ingot of this embodiment.

In one embodiment of the present invention, the casting apparatuscomprising a plurality of sides and a bottom defining a mold cavity,wherein the bottom has at least two surfaces, including a first surfaceand a second surface. The casting system further includes at least twometal feed chambers, including a first and a second feed chamber, eachfeed chamber adjacent to a different degasser, each degasser adjacent toa different filter. The casting system also includes at least one troughinto which each filter leads, that is adjacent to the mold cavity,wherein the trough includes at least one control apparatus between eachfilter and the mold cavity, the control apparatuses being structured tocontrol the flow rates of molten metal being fed into the mold cavity.In this embodiment, the bottom of the mold cavity comprises a substratehaving (a) sufficient dimensions, and (b) a plurality of apertures, suchthat the bottom: (i) allows cooling mediums to flow through theapertures and directly contact the metal, wherein a direction of theflow of the cooling medium is from the first surface of the bottom intothe mold cavity, and (ii) simultaneously resists the metal initiallypoured directly onto the second surface of the bottom from exitingthrough the apertures to the first surface of the bottom. Each feedchamber contains molten metal of different compositions. Molten metalfrom the first feed chamber is fed into a first degasser adjacent thefirst feed chamber. The molten metal from the first degasser is fed to afirst filter adjacent the first degasser. The molten metal from thefirst filter is fed into the mold cavity through the trough, wherein thecontrol apparatus between the first filter and the mold cavity is open.Before a desired thickness is reached in the mold cavity, molten metalfrom the second feed chamber is fed into a second degasser adjacent thesecond feed chamber. The molten metal from the second degasser is fed toa second filter adjacent the second degasser. The molten metal from thesecond filter is fed into the trough, wherein the control apparatusbetween the second filter and the mold cavity is closed. The controlapparatus in the trough between the first filter and the mold cavity isthen closed. The flow of molten metal out of the first feed chamber intothe first degasser is halted. Any metal between the feed chamber and thefirst control apparatus is drained. The control apparatus in the troughbetween the second filter and the mold cavity is opened thereby feedingthe molten metal from the second filter into the mold cavity. Before adesired thickness is reached in the mold cavity, the control apparatusin the trough between the second filter and the mold cavity is closed.The flow of molten metal out of the second feed chamber into the seconddegasser is halted, and the control apparatus in the trough between thesecond filter and the mold cavity is closed. Any metal between the feedchamber and the second control apparatus is drained. Molten metal fromthe first feed chamber is re-fed into the first degasser, and flows fromthe first degasser into an renewed first filter, and from the firstfilter into the trough. After a desired thickness is reached in the moldcavity, the control apparatus between the renewed first filter and themold cavity is opened, thereby re-feeding molten metal from the renewedfirst filter into the mold cavity. Simultaneously a cooling medium isdirected against the bottom of the mold cavity, whereby the molten metalis cooled unidirectionally through its thickness.

In another embodiment of the present invention the casting apparatuscomprises a plurality of sides and a bottom defining a mold cavity,wherein the bottom has at least two surfaces, including a first surfaceand a second surface. The casting system further comprises at least onemetal feed chamber adjacent to a mixing apparatus and at least onecontrol apparatus between the feed chamber and the mixing apparatus, thecontrol apparatus being structured to control the flow rates of moltenmetal being fed into the mixing apparatus. The casting system alsoincludes at least one filter between the mixing apparatus and the moldcavity and at least one control apparatus between the filter and themold cavity, the control apparatus being structured to control the flowrates of molten metal being fed into the mold cavity. The bottom of themold cavity comprises a substrate having (a) sufficient dimensions, and(b) a plurality of apertures, such that the bottom: (i) allows coolingmediums to flow through the apertures and directly contact the metal,wherein a direction of the flow of the cooling medium is from the firstsurface of the bottom into the mold cavity, and (ii) simultaneouslyresists the metal initially poured directly onto the second surface ofthe bottom from exiting through the apertures to the first surface ofthe bottom. The feed chamber and mixing apparatus each contain moltenmetal of different compositions. Molten metal is fed from the feedchamber to the mixing apparatus. Molten metal is fed from the mixingapparatus into the filter. Molten metal is fed from the filter into themold cavity. Simultaneously a cooling medium is directed against thebottom of the mold cavity, whereby the molten metal is cooledunidirectionally through its thickness. In another embodiment, themixing apparatus is a degasser that rotates at a constant speed. In yetanother embodiment, the casting system includes a degasser between themixing apparatus and the filter.

In yet another embodiment of the present invention, the castingapparatus comprises a plurality of sides and a bottom defining a moldcavity, wherein the bottom has at least two surfaces, including a firstsurface and a second surface. The casting system further comprises atleast two metal feed chambers, including a first and a second feedchamber and at least one trough into which each feed chamber leads,wherein the trough includes at least one programmable control apparatusbetween each feed chamber and a degasser located in the casting line,the control apparatuses being structured to control the flow rates ofmolten metal being fed into the degasser. The casting system alsoincludes at least one filter between the degasser and the mold cavityThe bottom of the mold cavity comprises a substrate having (a)sufficient dimensions, and (b) a plurality of apertures, such that thebottom: (i) allows cooling mediums to flow through the apertures anddirectly contact the metal, wherein a direction of the flow of thecooling medium is from the first surface of the bottom into the moldcavity, and (ii) simultaneously resists the metal initially poureddirectly onto the second surface of the bottom from exiting through theapertures to the first surface of the bottom. The feed chambers eachcontain molten metal of different composition. A first control apparatusbetween the first feed chamber and the degasser is programmed to permitmolten metal to flow into the degasser at a rate decreasing linearlyfrom a desired flow rate to 0 lbs/minute during a desired first castingperiod. A second control apparatus is programmed between the second feedchamber and the degasser to permit molten metal to flow into thedegasser at a rate increasing linearly from 0 lbs/minute to the samerate at which molten metal began flowing into the degasser from thefirst feed chamber during the first casting period. The first controlapparatus is also programmed to permit molten metal to flow into thedegasser at a rate increasing linearly from 0 lbs/minute to the rate atwhich molten metal began flowing into the degasser during the firstcasting period, during a desired second casting period. The secondcontrol apparatus is also programmed to permit molten metal to flow intothe degasser from the second feed chamber at a rate decreasing linearlyto 0 lbs/minute from the rate at which molten metal began flowing intothe degasser from the first feed chamber during the first castingperiod, during the second casting period. Molten metal is fed from thefeed chambers into the degasser through the trough, wherein the controlapparatuses control the flow as programmed. Simultaneously a coolingmedium is directed against the bottom of the mold cavity, whereby themolten metal is cooled uni-directionally through its thickness.

FIG. 1 is an illustration of one embodiment of the casting system of thepresent invention. In this embodiment, the casting system is a devicefor casting metal alloy products comprising: a system having at leastone source of material (1, 2, 3), each source having a feed trough (4,5, 6) leading to a mixer/degasser (10); a flow control valve (7, 8, 9)between each feed trough (4, 5, 6) and the mixer/degasser (10), whereinthe flow control valves (7, 8, 9) vary flows of material into themixer/degasser (10); another feed trough (11) leading from themixer/degasser to a filter (12); a final feed trough leading from thefilter to the casting apparatus (14).

In a further embodiment, the sources of material (1, 2, 3) arefurnace-reservoirs.

FIG. 2 is an illustration of another embodiment of the casting system ofthe present invention. In this embodiment, each feed trough (4, 5, 6)leads to a mixer (17); a flow control valve (7, 8, 9) is between eachfeed trough (4, 5, 6) and the mixer (10); another feed trough (18) leadsfrom the mixer (17) to a degasser (16); yet another feed trough (13)leads from the degasser (16) to a filter (12); finally a feed trough(15) leading from the filter to the casting apparatus (14).

Although the embodiments described in FIGS. 1 and 2 contain threeindependent material sources or furnace-reservoirs, any number ofindependent reservoirs could be used in any configuration needed toachieved the desired variations in ingot composition. In one embodiment,each furnace reservoir contains a binary aluminum alloy and the numberof reservoirs is equal to the number of alloy constituents needed. Forexample, to make a layered or gradient product containing Al—Zn—Mg—Cualloys, three reservoirs would be employed, one for each Al—Cu, Al—Mgand Al—Zn. In such an embodiment, any combinations of binary, ternary orthe quaternary alloys could be created. As a further example, an ingotcould be cast starting with a 5XXX alloy followed by a 2XXX alloy andfinally a 7XXX alloy. The transitions from the various compositionscould be sharp, resulting in a layered structure or gradual resulting ingradient structures. Other examples would include 5XXX/6XXX/2XXX or6XXX/7XXX/2XXX. Many other possibilities are clearly, possible.

FIG. 2 a is an illustration of an embodiment of the casting system ofthe present invention. In this embodiment, the composition of the ingotformed by the system is varied by flowing material from the first metalsource (1) through a trough (22) into another metal source (2), and thenthrough a trough (26) to the casting apparatus (14). The material mayoptionally flow from the second metal source (2) through a trough (23)to a degasser (16), then through a trough (24) to the casting apparatus(14); the material may flow from the degasser (16) through a trough (13)to a filter (12) and then to the casting apparatus (14) through a trough(15); the material may also flow from the second metal source (2)through a trough (25) to the filter (12) and then to the castingapparatus (14) through trough (15). In this embodiment, the ingot wouldstart with the composition in the second metal source and graduallytransition to the composition in the first metal source as the secondmetal source is diluted. The rate of change in composition can bechanged by varying the volume of metal in metal source (2).

FIG. 3 is an illustration of an embodiment of the casting apparatus ofthe present invention. In this embodiment, the casting apparatus (19)has a plurality of sides and a bottom (20) defining a mold cavity,wherein the bottom has at least two surfaces, including a first surfaceand a second surface; at least one control apparatus between the sourceof material and the mold cavity, the control apparatus being structuredto control the flow rates of molten metal being fed into the moldcavity, wherein the bottom comprises a substrate having (a) sufficientdimensions, and (b) a plurality of apertures (21), such that the bottom(20): (i) allows cooling mediums to flow through the apertures anddirectly contact the metal, wherein a direction of the flow of thecooling medium is from the first surface of the bottom into the moldcavity, and (ii) simultaneously resists the metal initially poureddirectly onto the second surface of the bottom from exiting through theapertures to the first surface of the bottom. A preferred diameter forthe apertures 21 is about 1/64 inch to about one inch.

A coolant manifold is disposed below the bottom (20) in one embodiment.The coolant manifold preferably is configured to selectively spray air,water, or a mixture of air and water against the bottom (20).

In a further embodiment, a laser sensor may be disposed above the moldcavity, and is preferably structured to monitor the level of materialwithin the mold cavity.

The application of coolant to the bottom of the mold cavity, along with,in some preferred embodiments, the insulation on the sides results indirectional solidification of the casting from the bottom to the top ofthe mold cavity. Preferably, the rate of introduction of material intothe mold cavity, combined with the cooling rate, will be controlled tomaintain about 0.1 inch (2.54 mm) to about 1 inch (25.4 mm) of moltenmaterial within the mold cavity 19 at any given time. In someembodiments, the mushy zone between the molten metal and solidifiedmetal may also be kept at a substantially uniform thickness.

FIG. 4 is an illustration of one embodiment of the casting system of thepresent invention. In this embodiment, the casting system is a devicefor casting metal alloy products comprising: a system having at leastone source of material (1); the source leading to a degasser (16); thedegasser leading to a filter (12); and the filter leading to the castingapparatus (14). In this embodiment, the resulting ingot has acomposition of a continuous gradient between metal of a firstcomposition originating in the metal source, and metal of a secondcomposition originating in the degasser. The rate of change incomposition can be changed by varying the volume of metal in metalsource (2).

In a further embodiment, the metal source (1), degasser (16), filter(12), and casting apparatus (14) are connected by feed troughs.

In yet another embodiment, the metal source (1) is a furnace-reservoir.

FIG. 5 an illustration of one embodiment of the casting system of thepresent invention. In this embodiment, the casting system is a devicefor casting metal alloy products comprising: a system having at leasttwo sources of metal (1, 2); the sources each leading to degassers (16);the degassers each leading to filters (12); the filter leading to atrough having two control apparatuses (27, 28); the trough leadingbeyond the control apparatuses (27, 28) to the casting apparatus (14).In this embodiment, the resulting ingot contains two different metals,each originating in one of the metal sources, and has a singlecomposition gradient through the thickness.

In a further embodiment, the metal sources (1, 2), degassers (16),filters (12), and casting apparatus (14) are connected by feed troughs.

In yet another embodiment, the metal sources (1, 2) arefurnace-reservoirs.

FIG. 6 an illustration of one embodiment of the casting system of thepresent invention. In this embodiment, the casting system is a devicefor casting metal alloy products comprising: a system having at leasttwo sources of metal (1, 2); the sources leading to a trough having twocontrol apparatuses (27, 28); the control apparatuses leading to adegasser (16); the degasser leading to a filter (12); the filter leadingto the casting apparatus (14). In this embodiment, the resulting ingotcontains two different metals, each originating in one of the metalsources, and has a continuous gradient composition across the thickness,for example the magnesium content.

In a further embodiment, the metal sources (1, 2), degasser (16), filter(12), and casting apparatus (14) are connected by feed troughs.

In yet another embodiment, the metal sources (1, 2) arefurnace-reservoirs.

Although the embodiments described in FIGS. 5 and 6 contains twoindependent material sources or furnace-reservoirs, any number ofindependent reservoirs could be used in any configuration needed toachieved the desired variations in ingot composition.

In one embodiment, and with reference to FIG. 11, a cast metal ingot 51is formed, wherein a solidification front remains substantially planarduring casting, wherein the ingot 51 has a top section 52, a middlesection 53, and a bottom section 54, as substantially shown in FIG. 11.In one embodiment, the bottom section 54 is composed of metal of a firstcomposition, the top section 52 is composed of metal of a secondcomposition, and the middle section 53 is composed of a mixture of metalof the first composition and the second composition.

In one embodiment, and with reference to FIG. 12, a cast metal ingot 61is formed, wherein a solidification front remains substantially planarduring casting, wherein the ingot 61 has a first layer 62, a secondlayer 63, a third layer 64, a fourth layer 65, and a fifth layer 66. Inone embodiment, the first and fifth layers 62, 66 are composed of metalof a first composition, the third layer 64 is composed of metal of thesecond composition, and the second and fourth layers 63, 65 are composedof a mixture of metal of the first composition and the secondcomposition.

In one embodiment, and with reference to FIG. 13, a cast metal ingot 71is formed, wherein a solidification front remains substantially planarduring casting, wherein the ingot 71 has a top section 72, a middlesection 73, and a bottom section 74. In one embodiment, the top andbottom sections 72, 74 are composed of a metal alloy of a firstcomposition, and the middle section 73 is composed of a mixture of thefirst composition and a second composition.

Although the methods of producing ingot have been described in detailwith reference to several embodiments, additional variations andmodifications exist within the scope and spirit of the disclosure.

1.-6. (canceled)
 7. A method of casting metal, comprising the followingsteps: feeding molten metal of a first composition into a mold cavity,via a first control apparatus, wherein the control apparatus is open,wherein the feeding comprises flowing out of a first feed chamber;closing the first control apparatus; opening a second control apparatus;feeding molten metal of a second composition into the mold cavity, viathe second control apparatus, wherein at least a portion of the metal ofthe first composition in the mold cavity is sufficiently molten so thatan initial feed of molten metal of the second composition mixes with themolten metal of the first composition in the mold cavity, wherein thefeeding comprises flowing out of a second feed chamber, wherein thesecond composition is different from the first composition; removing aningot from the mold cavity, wherein the ingot has a top section, amiddle section, and a bottom section, wherein the bottom section iscomposed of metal of the first composition, wherein the top section iscomposed of metal of the second composition, wherein the middle sectionis composed of a mixture of metal of the first composition and thesecond composition.